Re: Go off on a tangent

: : Regarding conversation, it means talk off topic. The person is talking about Subject 1 and gets distracted and starts talking about Subject 2. Or if a person is housecleaning, finds a box of old pictures and abandons the original job to research the photos, that's going off on a tangent. Tangent means "diverging from an original purpose or course" (Merriam-Webster).

: Quite right, but I wish Merriam-Webster had related the word to its original meaning. Tangent means, in L@tin, touching. Remember "Noli me tangere"? Most people encounter it in high school geometry, where two lines touch, but don't cross. Thus, going of on a tangent means going off on a line that touches the original one, but takes a different course. We're having, say, a discussion of hair-styling, and Barbara goes off on a tangent with a history of bobby pins. Hair-styling touches on bobby pins, but they are incidental to the main topic. : SS

Is there an idiomatic expression for intentional going off on a tangent as explained in the last case by SS? That is, going off on a different line in order to avoid a conversation on the original one? Thank you.